One system to control an engine during a condition of valve actuator failure is described in U.S. Pat. No. 6,278,932. The system description presents a way to control different cylinder banks of an engine that has individual valve actuator control units if data transmission between the actuator units and an engine control unit fail. Specifically, the individual actuator control units contain independent performance characteristics for operating valves, fuel injectors, and the ignition. For this operating mode, the communication link between actuator units must be functional. The actuator units also appear to rely on information provided by engine sensors in this operating mode. And, the system deactivates an entire cylinder bank if a single valve actuator fails.
The above-mentioned method can also have several disadvantages. Specifically, engine torque is likely to decrease when the operation of a single electrically actuated valve degrades. Since the method deactivates an entire cylinder bank, engine torque can be reduced by half. Further, although deactivating a bank of a six cylinder engine can produce an even firing engine, deactivating a bank of cylinders on an eight cylinder will produce an uneven firing engine. This can increase engine noise and vibration. In addition, the system also requires that data transmission between two actuator controllers be functional if the valve controllers are to continue operating during a communication failure between the engine controller and the valve controllers.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method that improves operation of an engine if communication between a valve controller and an engine controller degrades.